The following discussion of the background to the invention is intended to facilitate an understanding of the present invention. However, it should be appreciated that the discussion is not an acknowledgment or admission that any of the material referred to was published, known or part of the common general knowledge in any jurisdiction as at the priority date of the application.
Nuts and bolts are often used industrially as means of securing articles together (typically large scale equipment). In the case of mining equipment, one such use is as means of securing together a grinding mill.
A grinding mill typically uses a combination of grinding balls and water to mill ore. Due to the high impact nature of the process that takes place inside the grinding mill, the internal surface of the grinding mill is adorned with liner plates. These liner plates are typically installed by way of threaded bolts that penetrate the shell of the grinding mill. To facilitate this arrangement, a plurality of apertures are provided in the shell of the grinding mill.
As the size of the threaded bolt may not be known in advance, these apertures have to be of sufficient size to handle a variety of sized bolts. This leads to a further problem in that water, and other material, can then leak from the mill by way of the potentially large gap that is formed between the aperture and the bolt.
To prevent this leakage, a washer—referred to in the industry as a cup washer—is positioned in between the bolt and the nut. The washer must be of greater size than the aperture so as to seal off any gap that may be formed.
The problem with this arrangement is two fold:                When the mill needs to be disassembled for shutdown or other maintenance related purposes, the nut need first be removed to allow the cup washer to be removed thereafter;        The cup washer incorporates a sealing material (such as an elastomer), which due to the environment in which it is placed, often deforms and fails to seal off the aperture. At the very least this causes difficulties in seeking to remove the cup washer as well as potential leakage from the mill during operation.        
The end result of these problems is that significant time (generally in the order of five (5) to six (6) minutes) is spent in seeking to remove a single commonly used cup washer and nut. When considering that a mill may have upwards of three hundred (300) such cup washers and nuts about its surface, this means that any reduction in the time needed to remove a cup washer and nut will have significant productivity advantages.
In an attempt to achieve such advantages, one solution proposed is the cup washer retailed under the trade mark ELINGOL® by Ingenieria Innovaciones Technologicas (“IIT”) of Chile and the subject of Chilean patent application 182-2011.
The ELINGOL® cup washer is a substantially toroid shaped article. Protruding from the exterior surface of the toroid is an assembly projection. The assembly projection is designed to mate with a special tool and it is through the actions of this special tool that the ELINGOL® cup washer can be installed or removed as required.
The problems with this approach is as follows:                The nut still needs to be removed separately by means of conventional removal tools. This means that time can be lost where a single operator seeks to remove a cup washer due to the need to change between tools.        The maintenance worker needs to be in possession of the special removal tool. This further increases the costs of the system as a whole—not just in monetary terms, but also in terms of storage costs, safety, etc.        Due to the high torque and speed of the removal tool, if it is not properly mated to the assembly projection and disengagement ensues, there is significant potential for injury to the maintenance worker.        Even if properly mated, if the maintenance worker overruns the removal tool, the washer can completely disengage the bolt. This poses a potentially deadly situation as the washer may be projected by the engaging arm of the removal tool in a random direction.        
It is therefore an object of the present invention to create a combination of nut and washer that alleviates, if not completely solves, one or more of the aforementioned problems.